1. Field of the Invention
This invention relates to an apparatus for recording and/or reproducing an angle modulated signal and more particularly to an apparatus for recording and/or reproducing a wide band, angle-modulated signal after converting the signal into narrower band signals by dividing the channel thereof.
2. Description of the Related Art
Various information signal transmission systems have heretofore been developed for transmission of signals having wide bands. In the case of, for example, a video tape recorder arranged to record a signal of such a wide band as about 20 MHz as that of the luminance signal of a high quality television signal, it is very difficult to record the signal without compressing the band thereof. For recording a signal of such a high frequency, various losses such as a space loss and a gap loss greatly increase even if a relative speed between a magnetic head and a magnetic recording medium such as a magnetic tape is increased as much as possible. Besides, there are no known materials for the magnetic head that is capable of adequately operating at such a high frequency zone.
To solve this problem, it has been proposed to record or reproduce a high quality television signal of such a wide band by dividing it into narrow band signals of a plurality of channels and to have these narrow band signals recorded or reproduced respectively.
However, the above stated band compressing method inevitably somewhat degrades the picture quality of the original signal. Hence, the effective compressible extent of the band is limited. Further, the method of recording the original signal by dividing it into a plurality of channels necessitates use of, for example, a plurality of memories and a digital signal processing arrangement for channel dividing by writing or reading the signal into or from these memories under the control of a control circuit. The conventional method thus has resulted in a complex and expensive arrangement.
Meanwhile, another multi-channel method has been proposed. According to this method, a wide band information signal is frequency modulated; the timing of the rises and falls of the modulated signal are detected; timing signals thus obtained are frequency divided at different phases to obtain signals of a plurality of channels; and then these signals are simultaneously transmitted or recorded. The details of this method are as disclosed in U.S. Pat. No. 3,513,266 and Japanese Patent publication No. SHO 61-27946. This method makes a wide band information signal obtainable in a multiple channel with a relatively simple circuit arrangement.
However, with a wide band information signal recorded or reproduced by this method, it is impossible to obtain an adequately restored signal when any shift arises on the time base between a plurality of channels of reproduced signals due to the limited positional precision of recording/reproducing heads which varies between one apparatus and another. Therefore, this method necessitates a circuit for correcting the time base during a reproducing operation.